Quod Libet is a Gapless GTK+-based audio player written in Python. Its designed around the idea that you know how to organize your music better than we do. It lets you make playlists based on regular expressions (dont worry, regular searches work too).
Quod Libet Features
A distributed open source search engine and spider/crawler written in C/C++ for Linux on Intel/AMD.Discontinued
Outdated, no updates and website is down: https://github.com/gigablast/open-source-search-engine/issues/200